A roll toothbrush is a toothbrush manufactured by forming a rotary brush in a roller shape by stacking in multiple layers a substantially disk-shaped individual brush unit including radially bonded filaments made of a synthetic resin such as nylon, and rotatably resting the rotary brush on one end of a handle member of a toothbrush with a support shaft therebetween. Such a roll toothbrush has been commercialized as products for human use and products for use on pets such as dogs. In contrast to a general toothbrush with a bundle of filaments mounted in lines as bristles on one surface of a handle member at one end, this roll toothbrush is characterized by the ability to continuously massage gums with tips of the filaments while removing plaque and, moreover, being less likely to damage gingival, because of free rotating motion of the rotary brush in use.
A proposed method for manufacturing the individual brush unit that constitutes such a rotary brush (hereinafter referred to as “individual brush unit”) is, as disclosed in Patent Literatures 1 to 5, radially expanding one tip of a filament group that is a collection of filaments in a bundle, then heating and welding a core of the filament group to form the filament group into a substantial disk shape, and subsequently forming a shaft hole for passing a shaft through at the center of the disk. This method has been in practical use for manufacturing products. The invention disclosed in Patent Literature 4 was invented by the inventor of the present invention.
[Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2003-219911
[Patent Literature 2] Japanese Unexamined Patent Application Publication No. 2003-220080
[Patent Literature 3] Japanese Unexamined Patent Application Publication No. 2003-289947
[Patent Literature 4] Japanese Unexamined Patent Application Publication No. 2004-097692
[Patent Literature 5] Japanese Unexamined Patent Application Publication No. 2005-287842
A common feature of the techniques in these prior art documents is radially expanding on an anvil top surface a filament group protruding from an insertion hole of an anvil, by some expanding means, then welding a core of the expanded filaments by a welder separate from the expanding means, with the expanded filaments secured using a pressing member, and subsequently forming a shaft hole by cutting out the core with the use of cutting means that is also separate from the stated means, to complete an individual brush unit.
The cutting means of the prior art disclosed in Patent Literatures 1, 2, 3, and 5 has a cylindrical blade at a tip and is designed to cut out the core of the individual brush unit and cut off the individual brush unit from the filament group by moving downward into the insertion hole from above the anvil surface. In this regard, the cutting means of the prior art disclosed in Patent Literature 4 is different in that the cutting means has a cylindrical blade at a top end of a cylindrical member that houses and holds the filament group below the anvil, and is designed to cut out the core of the individual brush unit and cut off the individual brush unit from the filament group with the cylindrical blade moving into the insertion hole from below the anvil surface and brought into contact with a bottom surface of a tip of the welder placed further above.
Meanwhile, since welding remains are left on the tip of the filament group after the individual brush unit is cut off, another common feature of the techniques in these prior art documents is including cutting means that cuts off and removes the welding remains from the side. The cutting means of the prior art disclosed in Patent Literatures 1, 2, 3, and 5 is what is called a guillotine cutter embedded in the anvil so as to be horizontally movable, and is configured to cut off the welding remains on the tip of the filament group inside the insertion hole below the anvil top surface. In contrast, the cutting means of the prior art disclosed in Patent Literature 4 is an exposed sliding blade provided so as to be horizontally movable along the anvil top surface, which is different in that the cutting means is configured to cut off the welding remains on the tip of the filament group with the use of the cutting means and an edge surface of the insertion hole of the anvil.
Out of the techniques in these prior art documents, the expanding means of the prior art disclosed in Patent Literatures 1 and 2 for radially expanding one tip of the filament group is a cone having a conical tip which pushes and expands the tip of the filament group. The expanding means of the prior art disclosed in Patent Literatures 3 to 5 is air that is blown into one tip of the filament group so that the tip of the filament group is expanded by air pressure.
It is desirable that the filaments of the individual brush unit be manufactured so as to expand with a uniform density throughout the full circumference. However, the filament group protruding from the insertion hole of the anvil is not always a bundle with a completely uniform density, and even a slight displacement of the center of the expanding means from the center of a cross-section of the tip of the filament group leads to a failure to expand the filaments with a uniform density throughout the full circumference. Therefore, in both cases where the filaments are expanded by being pushed by the cone and where the filaments are expanded by being blown by air, there is a problem that defective products are manufactured due to a variation in the density of filaments, which is inevitably caused as long as the above-described expanding means of the prior art is used.
Furthermore, in the techniques in the prior art documents other than Patent Literature 4, when the cutting means is moved into the insertion hole of the anvil to cut out the core of the individual brush unit and cut off the individual brush unit from the filament group, the tip of the filament group is pushed into the insertion hole, with the result that pressure is applied to the filament group from above, leading to a risk of the filament group being bent or kinked in the insertion hole. Such bending or kinking causes a problem of not only reducing the smoothness of movement of the filament group when the filament group is fed out of the insertion hole so as to protrude on the anvil top surface for manufacturing a next individual brush unit, but also becoming an impediment to the expansion of the filaments on the anvil top surface with a uniform density throughout the full circumference.
Moreover, in the techniques in the prior art documents other than Patent Literature 4, the welder independent of the expanding means is used to weld the filament group, which necessitates horizontally moving the expanding means and the welder on a frame to interchange positions thereof according to a manufacturing process. Therefore, the manufacturing apparatus requires a mechanism that horizontally moves the expanding means and the welder to interchange positions thereof in addition to the mechanisms that feed the filament group, move the pressing member up and down, and move the expanding means and the welder up and down. This not only increases the number of steps and requires standby time for movement of the members, but also cannot help making the structure of the manufacturing apparatus complex. Thus, the manufacturing apparatus has a problem of a high initial cost and low productivity.